In a mobile communication system, when a signal transmitted from a transmitter is received via a wireless network, it is impossible to receive the signal which is not mixed with distortion or noise. Accordingly, various methods for solving such a problem have been suggested and a representative example thereof includes an error control coding method. In a CDMA mobile communication system which is one type of the mobile communication system, for example, a turbo code and a convolutional code are used as the error control coding method.
That is, channel coding may be used to correct an error generated in a process of transmitting data. At this time, parity data is generated in addition to information to be transmitted. Error correction capability of a channel coded code is improved as a ratio of parity data to the information to be transmitted is increased. That is, as a code rate of a transmitted bitstream is decreased, error recovery performance is improved.
However, if the code rate is decreased, the ratio of parity data to the information to be transmitted is increased and thus transmission efficiency is decreased in the communication system using a restricted resource. Accordingly, there is a need for a rate matching method which is capable of flexibly matching a code rate according to a communication state.
In the UMTS standard defined by the 3rd Generation Project Partnership (3GPP) in Release '99, rate matching is performed with respect to code bits outputted after channel coding. Mostly, the number of code bits outputted after channel coding is not matched with the total number of bits in a wireless transmission unit (TU). The rate matching indicates an operation for performing repetition or puncturing with respect to the code bits and matching the number of code bits with the total number of bits in the wireless TU. The rate matching may be used in various standards such as the High Speed Downlink Packet Access (HSDPA) standard.